Segmented magnetic armature for phonograph pickups



May 22, 1951 2,553,715

SEGMENTED MAGNETIC ARMATURE FOR PHONOGRAPH PICKUPS Filed Aug. 12, 1947G. L. MII LER 2 Sheets-Sheet 1 INVENTOR v ATTORNEYS May '22, 1951 FiledAug. 12, 1947 G. L. MILLER 2,553,715

SEGMENTED MAGNETIC ARMATURE FOR PHONOGRAPH PICKUPS 2 Sheet-Sheet 2azjlzizzer" INVENTOR 1 t BY f I I I 0 ATTORNEYS Patented May 22, 1951UNITED STATES 1+ PATENT OFFICE SEGMENTED MAGNETIC ARMATURE FOR PHONOGRAPH PICKUPS George L. Miller, Hackensack, N. J.

Application August 12, 1947, Serial No. 768,173

This invention relates to an audio frequency unit which is designed witha novel magnetic circuit for use in recording, or reproducing,phonograph pick-ups but which is easily adaptable for incorporation inearphones, speakers, and other similar actuator equipment.

The primary object of this invention resides in the provision of animproved magnetic circuit unit which will permit a wide variation inarmature design.

Another object of this invention lies in the provision of variousdesigned armatures for use with the improved magnetic circuit whichextend the resonance of the unit to new limits thereby tending tocompletely eliminate note distortion and greatly increase the value ofall notes especially the higher and lower notes which are greatlydistorted and depreciated in value by present day units which cannothandle or control the wide differences in frequency and vibration rateswhich are encountered by the needle when tracking the average recording.This unit is capable of reproducing very wide ranges at their true tonalqualities with the additional reproduction of the heretofore completelylost overtones.

Still another object of this invention lies in the provision of an audiofrequency unit provided with an improved supporting pick-up arm andflexible base therefor which improves the action of the unit and dampensany record noise which would be transmitted to the cabinet.

Still further improvements and objects of this invention will readilyappear to those skilled in the art and science when the followingdescription is read in the light of the accompanying,

drawings in which:

Fig. 1 is a side elevation of the pick-up unit.

Fig. 2 is an enlarged vertical section of the magnetic pick-up unit.

Fig. 3 is a vertical section of the arm supporting base.

Fig. 4 is a vertical section taken on line 4-4 of Fig. 2.

Fig. 5 is a horizontal section taken on line 5-5 of Fig. 2.

Fig. 6 is a perspective plan View of the preferred armatureconstruction.

Figs. 7 and 8 are perspective views of modifications -of the armatureshown in Fig. 6.

I wish it to be understood that I contemplate any and all modificationsof the magnetic circuit and of the flexible armature, which are to behereinafter set forth, which fall within the scope of the appendedclaims, together with other 3 Claims. (Cl. 179100.41)

2 structural modifications directed to materials, sizes and generalcharacteristics.

Referring now to the accompanying drawings which are merely illustrativeof the invention and in which like characters indicate similar partsthroughout, A designates the supporting base for the pick-up arm B whichcarries at its outer extended end the audio frequency, magnetic, pickupunit 0.

The pick-up arm supporting base A comprises a housing I flanged at itsbase as at 2 to permit it to be' firmly secured in a phonograph unit.The top of the housing I is provided with a circular opening 3 centrallyformed therein and a felt, sponge rubber, or like bushing 4 secured, bya split ring 5, or the like, within said housing beneath andunderlapping the opening 3. A tube 6 is vertically seated in the bushing5 and secured by a flat flange l, resting on the bushing top, and a lockcollar 8, secured thereabout beneath the bushing, within the housing.

lhe tube 6 is universally coupled to the'pickup arm B by an extension 9which'permits the circuit wires 10, from the magnetic pick-up C whichare carried within the arm B, to be passed downwardly through the tube 6into the housing where they are led to the speaker circuit.

The pick-up unit C, which comprises the principal embodiment of thisinvention, is composed of a hollow rectangular unit housing 20, with oneenlarged face thereof being open, which is rigidly affixed to theextended end of the pick-up arm B by a Welded joining of the closedenlarged face vertically with an angularly formed termination of thearm, substantially as illustrated in Fig. 5.

a This arrangement places the open face of the unit housing in avertical plane away from the arm.

An elongated neutral pole piece 2| of solid, laminated or powdered ironconstruction, is perpendicularly secured to the contact plate 2|centrally intermediate its height to dispose the pole longitudinallywithin the housing.

This pole piece terminates at equally spaced distances from the opposedends of the housing, and is provided with a longitudinal knife-edge 22projecting slightly beyond the open face of the housing,

A single coil 23 is wound on the neutral pole and lies entirely withinthe housing. This coil is tied to the circuit wires I0 brought to, theunit.

- housing through the pick-up arm B.

A pair of elongated permanent bar magnets 24 are, placed in the unithousing one adjacent each longitudinal side wall of the housingparalleling the neutral pole piece and each being separated;

tions with their fields opposed, north to south,-

as shown in Fig. 4, this providing a, short magnetic circuit withexcellent keeping qualities, while a heavy construction of the centralneutral pole 2| will provide a better magnetic saturation of the entirecircuit.

Extension pieces 25 are secured to the outer ends of the permanentmagnets, exposed at the open face of the housing, which for a spaceddistance project transverse the open face overlying a portion of thecoil 23 and providing a greater and more positive attraction area to thearmature which is to be described.

In audio frequency pick-up units of the same general type as thatheretofore described a rigid single piece armature has been used inconjunction with a pair of pole pieces in such a manner as to vibratetherebetween, with needle impulses conveyed thereto, to induce varyingE. M. F. in a coil to be converted by a speaker unit to the notes ortones being reproduced from a record. However the resonance reproductionof such a unit is limited by the inability of the rigid armature toaccommodate the greatly varied vibrations, When the needle of such aunit encounters a high note, in recording or reproducing, the armaturemoves at a high rate of speed thereby inducing an extremely high E. M.F. in the coil and causing an over emphasis of the note. Inversely thesame is true with a reduced armature action with the lower notes whichcauses a greatly reduced E. M. F. in the coil and a loss of the lownotes. Consequently, the net result of such a unit is a distorted,unbalanced quality of the reproduction, or recording, as a whole.

The armature system that I propose and introduce turns the undesirablecharacteristics of such a magnetic unit to advantage in providing a unitof substantially unlimited resonance which is free from distortion andwhich produces high tonal quality.

The structure of this improved unit incorporates an armature or movableelement 26 which is composed of a single flexible unit, or two separateunits 25a and 26b connected by a flexible linkage with the needle 21being rigidly connected to thatunit of the two, or portion of theflexible unit, designed to have a higher fundamental period ofvibration.

, The Figs. 6 through 8 illustrate the possible constructions of thisarmature with Fig. 6 disclosing the separate units 26a and 26b, the unit7 26a being of a lighter construction than unit 261).

When the armature, unit disclosed in Fig. 6 is used in the unit, asshown in Fig. 5, the smaller unit, 25a, is longitudinally balanced onone end portion of the knife-edge 22 of the neutral pole disposing theneedle, which is removably carried in a housing D formed integrally withthe unit, beyond the unit housing. The second portion, 26b, of thearmature is similarly balanced on the remaining portion of theknife-edge with a reduced portion thereof overlying the first portion26a, being spaced thereabove by a plain rubber spacer 28. The two unitsare then secured to the neutral. .pole, in their balanced positions, bya pair of studs 29, one of which passes through enlarged holes, whichpermit the units to seesaw, in the overlapping sections and the spacer'28 into the neutral pole, and the second stud which passes through theenlarged unit into the pole. Each of the studs are provided with spongerubber or like washers between the armature and their head portions thusproviding a damping action but allowing accurate counteraction of themagnetic pull without sacrificing sensitivity of the unit.

The modifications of the armature shown in Figs. '7 and 8 includerespectively, a single piece made into a pair of flexible units 30 and3| by a pair of parallel, overlapping transverse slots 32; and a singleunit 33 tapered in thickness throughout its length.

Keeping in mind those armature forms illustrated the operation of theunit is as follows.

As the needle travels its course that section of the armature carryingthe needle, and having a greater fundamental vibration period, willfollow impulses imparted thereto at all frequencies and, when the needlecontacts a high note this first section, having a higher fundamentalperiod of vibration, will follow the exact tone frequency. However,inability of the flexible connection between the sections to follow thegreat vibration speed of this first section will cause the heaviersection, or portion, to remain idle, or substantially so, thuspreventing an increase in the coil induced E. M. F. sufficient to causean overemphasis and distortion of the high note and thereby reproducingthe note with superior tonal quality. Inversely with contact of a lowernote by the needle the reduced vibration of the first section or portionwill produce sufiicient inertia in the flexible coupling to causevibration of the heavier section, or portion, thus re-enforcing the E.M. F. to produce a true note on the lower scale which otherwise would belost.

Thus it may be seen that an improved and novel audio frequency magneticpick-up unit has been provided with the heretofore set forth objects andadvantages.

Having thus described and explained the structure and function of thisinvention what I desire to claim in Letters Patent is:

I claim:

1. An armature for audio frequency magnetic pick-ups comprising asegmented unit the segments of the unit being of different weights,securing the unit to a neutral pole support, and one of said studsconnecting the segments of the armature units whereby said segments ofthe armature have fundamental periods of vibration.

2. An armature for audio frequency magnetic pick-ups, comprising asegmented unit, the segments of the unit being of different weights, thesegments being aranged in overlapped spaced relation with respect toeach other, and means for securing the segments to a pole piece, wherebythe periods of vibration of said armature segments are fundamentallydifferent.

3. An armature or. movable element for frequency magnetic pick-ups, forpositioning on a neutral pole piece, comprising a unit embodying aheavy. segment and a substantially light segment, the heavy segmenthaving a cut-away portion in the lower surface thereof extendinginwardly from one end thereof, a bolt extending through the heavysegment adjacent to the opposite end thereof, securing the heavy segmentto the neutral pole piece, said substantially light segment beingdisposed within the cutout portion in spaced relation with the surfaceof the heavy segment, and a bolt passing through the segments connectingthe segments with the neutral pole piece, providing a flexible armaturewith segments having periods of vibration fundamentally diiferent.

"GEORGE L. MILLER.

(References on following page) REFERENCES CITED The following referencesare of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Hutter Jan. 6, 1931 McClatchieDec. 8, 1931 Burt Sept. 6, 1932 Niumber f; 1 1,975,907

Sollie Jan. 23, 1934 10 6 Name Date Strauss Oct. 9, 1934 Miller Apr. 14,1936 Bender Aug. 24, 1937 Edwards June 20, 1939 Thompson Nov. 19, 1940Bruderlin Oct. 30, 1945 Reason Apr. 16, 1946 Baker June 24, 1947

